M. Coli

Integrated geological-architectural pilot study of the Biet Gabriel-Rufael rock hewn church in Lalibela, northern Ethiopia

We present a geological and architectural integrated pilot study, aiming at the preservation of the Biet Gabriel-Rufael church, located in Lalibela, the worldwide known Ethiopian rock hewn monumental site protected by UNESCO since 1978. The town developed since the Neolithic up to the medieval age, as inferred from the traces of three distinct architectural phases. Lalibela was built on a geological substratum made of rocks belonging to the Ethiopian Plateau suite, which is mainly composed of basalts of fissural origin or derived from shield volcanoes. The geological units are composed of alternating massive and scoriaceous basalts. The main scoriaceous basalt level, embedded within the massive basalts, is 30–40 m thick and corresponds to the horizon within which the Biet Gabriel-Rufael church all the other monuments of Lalibela have been carved. Therefore, the evolution of the town was strongly conditioned by the occurrence and extent of the softer scoriaceous basalt level. Many fracture systems of both natural (i.e. geological) and anthropic origin (these latter connected to the carving of the church), were recognized. The fracture pattern determined the subdivision of the church into different blocks that can behave independently, thus compromising the stability of the monument. A net of deformometers and fracture gauges was installed for the monitoring of the fracture system and a preliminary Finite Element analysis, following the approach used for underground excavations, was performed, with the aim of elucidate the mechanical behaviour of the rock. The integration between geo-mechanical approach to the rock mass and the architectural study of the critical situation due to the carving and connected to buildings, resulted in the precise individuation of future interventions devoted to the conservation of these monuments.

Tunnelling and Hydrogeological Issues: A Short Review of the Current State of the Art

Since the 1960s, there has been an increasing interest in the understanding of the hydraulic flow inside a hard rock mass, since water inflow into deep tunnels constitute a hazard, in addition to being an important factor in controlling the advancement of excavation. The characterisation of fluid flow through hard rock masses is still one of the most challenging problems faced by geologists and engineers. A rock mass is characterised by networks of discrete and ubiquitous discontinuities that strongly affect its hydraulic properties, but detailed knowledge of the discontinuity properties allows for the evaluation of the hydraulic flow in the rock mass affected by the excavation of a tunnel. A geostructural field survey is fundamental in order to correctly define the discontinuity types, settings and networks. Numerous approaches have been proposed to estimate the water inflow based on empirical relations supported by field experience and case studies, as well as analytical solutions. Often, however, these approaches are not easily applicable in standard practice and in complex scenarios. The most appropriate approach to characterising the hydraulic flow of the rock mass and to predicting in the most effective way the expected water inflow during the excavation of a tunnel is based on a detailed geological model and geostructural analysis as described in this paper.

THE MARBLE BEACHES OF TUSCANY

ABSTRACT. Beach‐nourishment operations designed to replace sediment lost through erosion change the identity and meaning of coastal landscapes. Seven beaches in Tuscany, nourished with marble‐quarry waste, reveal how an industrial byproduct is naturalized by particle rounding and sorting and can become a positive symbol of human‐altered nature. The marble was placed on formerly sandy beaches, resulting in different grain size and color of sediments, beach morphology, and value for human use. The abrasion rate of marble makes the nourished beaches unsatisfactory when viewed solely as protection structures, but the rapid particle rounding and aesthetic appeal of marble increase the acceptability of the beaches for recreation.

Vein distribution in a thrust zone: a case history from the Northern Apennines, Italy

Abstract In the Northern Apennines the Cervarola Thrust superposes the Cervarola Unit (Early-Middle Miocene sandstones and shales) on the Marnoso Arenacea Unit (Middle-Late Miocene marly sandstones) and has the geometry of a leading imbricate fan. Each thrust sheet consists of a thick turbiditic sandstones sequence (Mt Cervarola Fm.), which grades downward into shales (Scisti Varicolore Fm.). During thrusting, the Scisti Varicolore Fm. was intensely deformed and widely affected by shear veins, filled with calcite. A regional pattern has been detected in the vein distribution: veins are concentrated some ten metres above the thrust fault, in a band a few metres thick, and can be grouped into two systems. The principal one presents two sets of veins striking in the same direction as the thrust: one set dips at a high angle to the thrust fault (High Angle Set, HAS), whereas the other one lies sub-parallel to the thrust fault (Low Angle Set, LAS). Both of these sets of veins have dip-slip slickenfibres. The secondary system comprises two other sets of veins, which lie obliquely to the thrust fault. Slickenfibres are strike-slip and trend nearly parallel to the thrusting direction and to the intersection lineation between the two sets. Vein development can be explained in the light of the fluid-dynamic studies recently developed for present-day accretionary prisms.

Pietra Serena Mining in Fiesole. Part II: Geological Situation

The results are presented for the investigations into the geological estimate of Macigno formation representing an Oligocene-Miocene turbiditic sequence of the Northern Apennines, from the coarse-graded beds of which the “Pietra Serena” quarry stone was mined. It is shown that the sedimentological features, the physico-mechanical properties, and the mineralogical composition of rocks govern the distinctions in the operating performances.

Pietra Serena Mining in Fiesole. Part I: Historical, Cultural, and Cognitive Aspects

Within comprehensive investigation of Fiesole area (Italy), scientific, technical, and cultural aspects are considered for mining and using the traditional “Pietra Serena” stone geologically known as quarry stone.

Synergistic and Interdisciplinary Approaches for the Conservation of Monumental Heritage: Cupola of Santa Maria del Fiore in Florence, Italy

AbstractThis paper presents the results of an interdisciplinary study carried out on Brunelleschi’s Cupola of Santa Maria del Fiore in Florence, Italy, one of the most emblematic masonry domes in the world. The cupola has been affected since the beginning of its construction by a widespread cracking phenomenon, and several studies were done over the centuries to clarify its safety conditions. To have a direct and indirect record of the cracks opening or closing, a complex monitoring system was installed on the monument during the last century. An accurate analysis of crack widths and global displacements, performed considering both historical and recent monitoring data, has allowed for the identification of the movements developed in the monument, evaluating their relationship with environmental and seismic events. In line with the interdisciplinary approach strongly recommended in the field of assessment and conservation of monumental heritage, this paper reconsiders some issues concerning the causes of ...

Dynamic Response of the Giotto's Bell-Tower, Firenze, Italy

An ambient vibration survey of a structure represents an efficient and accurate technique for the characterization of its dynamic response to wind and seismic excitation. The dynamic response of the Giotto’s bell-tower has been monitored with four velocimetric stations placed along the tower. The frequencies values and modal shapes have been evaluated by analyzing the data in the frequency domain and time domain respectively. Two translational modes for each direction and a torsional mode have been detected. An iterative back-analysis procedure has been set up to define a realistic elastic modulus of the stone masonry. The soil-structure interaction has been included in the identification process. The elastic modulus of the stone masonry represents an important mechanical parameter for the definition of reliable finite element models of the structure, that could be an useful tool for further investigations on the tower seismic behavior.

Rivisitazione geologica della grande Galleria dell'Appennino

The railway connections between the Po area and the central Tyrrhenian part of Italy had already been in place since the XIX century with the Pontremolese, Porrettana and Faentina railway lines; but these lines did not offer, either singularly, or together, a capable, rapid and economic means of transit needed for the amount of traffic that went along the axis of the Peninsula (DE MARTINO, 1934). In order to overcame these limitation the Eng. Protche project was considered the best, the Apennines would have been crossed by means of a great 18.023 m tunnel, with a pass at a height of 328 m above sea level, and would have slopes reaching of no more than 12‰.During the time of construction of the Great Tunnel the geological setting of the Apennines followed the classic Tuscan geological school of thought (MADDALENA, 1929, 1933; SACCO, 1934) (fig. 5) which ordered the different layers from highest to lowest: 1a) alternated layers of sandstones with slates; 1b) marly Limestone with interposed slates; 2a) Slates and Argille Scagliose (with interposed ophiolitic rocks); 2b) arenaceous schists, sandstone and marls with alternations of argillaceous schists and marly limestone; 3) Sandstones (hard sandstone) in thick beds, regularly alternating with argillaceous-arenaceous schists.GEOLOGICAL KNOWLEDGE TODAY Geological studies of last the 40 years have come to subdivide the «Argille Scagliose» (SALMOJRAGHIi, 1881; MERLA, 1951) that constitutes a good part of the Padana-Bolognese Apennines in several units which are part of the external Ligurian Units (ABBATE et alii, 1969) and the «Chaotic Complex» (TAWNY, 1973; ABBATE & SAGRI, 1982). Recent geological study and survey (BETTELLI & PANINI, 1987; BETTELLI et alii, 2002; Panini et alii, 2002; Sheet 252 Barberino del Mugello and Sheet 237 Sasso Marconi, scale 1:50.000) have brought about distinctions also within the «Chaotic Complex» itself. The geological setting along the tunnel is summarised in tab. 1.GEOLOGICAL SECTION IN THE AXIS OF TUNNEL Based on the excavation reports of the Great Tunnel of the Apennines, including the lithological description of the rock masses crossed and the present knowledge of the geological order, a geological section was designed (tav. 1; original in a scale of 1:10.000) that aids in reinterpreting the geo-structural order of the rock masses crossed by the tunnel.Swelling Digging that occurred in predominantly argillaceous formations and that was strongly tectonic was hindered because of a strong pressure coming from the terrain and pushing against the support system and the wall coverings; the stretch of the tunnel that had the most problems when digging because of the phenomenon of swelling was the 600 m, between PK 2.380 and 3.000 from the north in the «Argille Scagliose» (AVC).Grisou During the digging of the Great Tunnel of the Apennines very light to abundant gas emissions manifested themselves in rock masses where the argillaceous element predominated and above all in the «Argille Scagliose» (now AVC and APA). Based on the information found in several articles and reports, there were two types of gas emissions: high and low pressure. The high pressure emissions, were in general unexpected, with remarkable capacities and were connected to calcareous and arenaceous elements that were fractured and deformed as found in stone within the argillaceous formations, Argilloso-Calcarea Unit (AVC). The low pressure emissions were of a modest capacity and occurred in rock masses that were mostly argillaceous.Most of the gas emissions registered took place in areas associated with faults, fractures and thrusts, that is, components that are prevalently vertical allowing a means of escape for gas coming from the deep underground.Water In the Great Tunnel of the Apennines, water infiltration was more frequent at the southern entrance of the tunnel characterized by the presence of sandstone. The only exception was in the first 780 m from the southern entrance where «Scisti Galestrini» alternately crossed with sandstones (Formation delle Marne Varicolori di Villore, MVV).The water flow found in the tunnel was influenced by a direction-orientation of discontinuities, with the water flow concentrated along the overhead plains and in areas that were intensely fractured and detensionate. The water capacity in the tunnel gallery diminished with the passing of time and after the completion of the covering of the walls there remained no trace. As a whole, the water infiltrations evoked difficult interventions such as pumping out water. It also involved security issues, delays in the works and increased costs and a large impact on the water resources of the area, that only after many years has found an equilibrium.CONCLUSIONS The geological re-visitation of the Great Tunnel of the Apen-nines has allowed us to review its geological order at the axis of the tunnel, as well as reinterpret the excavation data in light of the geological knowledge that we have today about the area. In addition, it allowed us to delineate a geological order of the underground based on a sort of horizontal survey, which helped to calibrate and verify geological orders and hypotheses deriving from the new surface geological data. Knowing the history of the critical geological situation aided in comparing that which was encountered during the recent TAV and VAV works, which was found to be identical. This present work, besides contributing to the history and demonstrating the significance of a complex work such as the Great Gallery of the Apen-nines, also shows how a critical and contemporary re-reading of past experiences can greatly contribute in the phase of planning more complex works in the same geological context.